Safety, virology and pharmacokinetics of oseltamivir in infants with laboratory-confirmed influenza: a Phase I/II, prospective, open-label, multi-centre clinical trial

Management of influenza - updated Swedish guidelines for antiviral treatment

Influenza causes seasonal epidemics of respiratory infection in all parts of the world. Manifestations of influenza range from mild upper to severe lower respiratory tract infection. Medical risk groups are defined by factors predisposing for development of severe disease and are recommended annual vaccination as a protective measure. The previous Swedish treatment guidelines for influenza were issued in 2011, and a review of current evidence was deemed relevant. An important reason to revisit the guidelines is the recent approval of a novel drug for influenza treatment, baloxavir. Updated Swedish evidence-based guidelines created by a group of experts from various research areas, for the management of influenza are presented here. The work has been made in collaboration with the Public Health Agency of Sweden and the Swedish Reference Group for AntiViral therapy (RAV). The updated guidelines include guidelines for diagnostics, treatment and prophylaxis in special groups, including management of pregnant women and children with influenza. A new section about infection control has been added. Pharmacological treatment is covered in detail with regards to indication and dosage. Additionally, drug resistance and environmental aspects are discussed.

Dosing regimen optimisation for oseltamivir in immunocompromised paediatric patients with influenza: Extrapolation of efficacy

AIMS

To optimise the dosing regimen of oseltamivir for immunocompromised (IC) paediatric patients (<18 years) with influenza, we used an extrapolation approach alongside clinical data.

METHODS

Efficacy was extrapolated from adult IC patients to paediatric IC patients by leveraging existing efficacy, safety, pharmacokinetic (PK)/pharmacodynamic (PD), and disease-progression models of oseltamivir and oseltamivir carboxylate (OC). Data of IC paediatric patients from two studies (NV25719 and NV20234) were included in the population PK (n = 30), PK/PD analysis (n = 22) and disease modelling approach (n = 36). Simulations were performed to identify the optimal dosing regimen.

RESULTS

Clearance of oseltamivir (CL) and OC (CL_M ) were similar in IC and otherwise-healthy (OwH) patients <10 years, but decreased by 44.4% (95% CI: 26.8-62.0) and 49.1% (95% CI: 34.5-63.8), respectively, in IC patients aged 10-17 years versus OwH patients. There were no notable exposure-response relationships for any of the virologic PD analyses. Thus, no additional benefit was seen with oseltamivir carboxylate exposures higher than achieved with the conventional dose (75 mg twice daily, age- and weight-adjusted for children <13 years). The disease model illustrated that doses above the conventional oseltamivir dose had limited impact on viral kinetics in IC paediatric patients and a prolonged treatment duration of 10 days was favoured to limit potential viral rebound.

CONCLUSION

An oseltamivir dosage recommendation (conventional dose, twice daily for 10 days) was established in IC paediatric patients with influenza, based on extrapolation of efficacy from IC adults, leveraging population PK, PK/PD, and disease modelling, whilst taking resistance and safety data into account.

Efficacy and Safety of Oseltamivir in Children: Systematic Review and Individual Patient Data Meta-analysis of Randomized Controlled Trials

Background

Oseltamivir has been used to treat children with influenza for nearly 2 decades, with treatment currently approved for infants aged ≥2 weeks. However, efficacy and safety remain controversial. Newer randomized, placebo-controlled trials (RCTs), not included in previous meta-analyses, can add to the evidence base.

Methods

We conducted a systematic review to identify RCTs of oseltamivir therapy in children. We obtained individual patient data and examined protocol-defined outcomes. We then conducted a 2-stage, random-effects meta-analysis to determine the efficacy of treatment in reducing the duration of illness, estimated using differences in restricted mean survival time (RMST) by treatment group. We also examined complications and safety.

Results

We identified 5 trials that included 2561 patients in the intention-to-treat (ITT) and 1598 in the intention-to-treat infected (ITTI) populations. Overall, oseltamivir treatment significantly reduced the duration of illness in the ITTI population (RMST difference, -17.6 hours; 95% confidence interval [CI], -34.7 to -0.62 hours). In trials that enrolled patients without asthma, the difference was larger (-29.9 hours; 95% CI, -53.9 to -5.8 hours). Risk of otitis media was 34% lower in the ITTI population. Vomiting was the only adverse event with a significantly higher risk in the treatment group.

Conclusions

Despite substantial heterogeneity in pediatric trials, we found that treatment with oseltamivir significantly reduced the duration of illness in those with influenza and lowered the risk of developing otitis media. Alternative endpoints may be required to evaluate the efficacy of oseltamivir in pediatric patients with asthma.

Advancing challenges in Paediatric Virology: An interview with Professor Barbara A. Rath, Co-founder and Chair of the Vienna Vaccine Safety Initiative

The Vienna Vaccine Safety Initiative (ViVI) is an international, scientific, non-profit, research organization, which aims to promote research, clinical practice and communication on Paediatric Infectious Diseases (PID) in a globalized healthcare setting, to facilitate the implementation of high standards in vaccine safety and efficacy and to support international and interdisciplinary scientific collaboration. Professor Barbara A. Rath, Chair and Co-founder of the Vienna Vaccine Safety Initiative, advocates for the establishment of global research networks in the field of neonatal and paediatric viral infections. Viruses do not respect borders, and large datasets are required and joint action is necessary to further strengthen efforts towards viral diseases eradication and prevention. She encourages the paediatric community to embrace the new opportunities technology offers for healthcare and medical education. To date, the Vienna Vaccine Safety Initiative has developed a number of innovative mobile applications and diagnostic tools, such as the 'VAccApp', which helps parents understand which vaccines were administered to their children, the 'ViVI Disease Severity Score', which measures clinical severity in patients with acute respiratory infections and flu-like illnesses, the 'VACC Tool', which assesses patient's clinical presentation to a set of diagnostic algorithms for adverse events following immunization and the 'ViVI Health Survey', which enables children and young adults on the move to report health needs securely and confidentially. Professor Rath agrees that during this decade there is momentum in the field of Paediatric Virology, as new antivirals and vaccines emerge and are finally becoming available to children. In the future, 'in-house' specialists for Paediatric Virology could be helpful to provide quality of care and reduce antimicrobial resistance by providing individual as well as hospital-wide consultations and advice. She estimates that Paediatric Virology will eventually find its place in the context of PID and Vaccinology.

Prospective surveillance of antiviral resistance in hospitalized infants less than 12 months of age with A(H3N2) influenza infection and treated with oseltamivir

BACKGROUND

Infants exhibit elevated influenza virus loads and prolonged viral shedding, which may increase the risk for resistance development, especially in cases of suboptimal exposure to antiviral therapy.

METHODS

We performed a prospective surveillance of hospitalized infants undergoing oseltamivir therapy during the 2008-2009 and 2011-2012 influenza seasons at two paediatric hospitals in Germany. A total of 37 infants less than 1 year of age with laboratory confirmed influenza A(H3N2) infection received oseltamivir as per physician's order for 5 days (2008-2009 season: 2 mg/kg twice daily; 2011-2012 season: 2.0 mg/kg; 2.5 mg/kg and 3.0 mg/kg twice daily for infants <1 month; 2-3 months and 4-12 months, respectively). Virus load, the susceptibility to neuraminidase inhibitors (NAIs), and the presence of molecular markers of resistance to NAIs was assessed for influenza viruses recovered from respiratory samples collected at baseline and during follow-up visits.

RESULTS

Overall, 73% of the infants continued to shed viral RNA detectable by reverse transcription (RT)-PCR after dose number 10 of oseltamivir; 12 infants shed viruses, 2 of them (both 9 months of age) shed resistant viruses. Resistance was characterized by ≥1,000-fold increase of 50% inhibitory concentration (IC₅₀) for oseltamivir, up to 50-fold for zanamivir and elevated Km values when compared to susceptible A(H3N2) strains. Sanger sequencing revealed the selection of the NA-R292K substitution in both instances (after dose number 10 on day 6).

CONCLUSIONS

Our data suggest that it may be relevant to monitor antiviral resistance systematically in all infants, considering that the European Medicines Agency has recently extended the licensure for oseltamivir to include full-term infants.

Oseltamivir for influenza infection in children: risks and benefits

Influenza is a common disease affecting many children each year. In a number of cases, particularly in children <2 years old and in those with severe chronic underlying disease, influenza can be complicated by lower respiratory tract infections, acute otitis media, rhinosinusitis, febrile seizures, dehydration or encephalopathy. Oseltamivir is the influenza virus drug that is most commonly studied in children for both the treatment and prevention of influenza. To avoid the risk that children with mild influenza or patients suffering from different viral infections receive oseltamivir, oseltamivir treatment should be recommended only in severe influenza cases, especially if confirmed by reliable laboratory tests. However, therapy must be initiated considering the risk of complications and the presence of severe clinical manifestations at age- and weight-appropriate doses. Because the vaccine remains the best option for preventing influenza and its complications, prophylaxis using oseltamivir should only be considered in select patients.

Oseltamivir Population Pharmacokinetics in the Ferret: Model Application for Pharmacokinetic/Pharmacodynamic Study Design

The ferret is a suitable small animal model for preclinical evaluation of efficacy of antiviral drugs against various influenza strains, including highly pathogenic H5N1 viruses. Rigorous pharmacokinetics/pharmacodynamics (PK/PD) assessment of ferret data has not been conducted, perhaps due to insufficient information on oseltamivir PK. Here, based on PK data from several studies on both uninfected and influenza-infected groups (i.e., with influenza A viruses of H5N1 and H3N2 subtypes and an influenza B virus) and several types of anesthesia we developed a population PK model for the active compound oseltamivir carboxylate (OC) in the ferret. The ferret OC population PK model incorporated delayed first-order input, two-compartment distribution, and first-order elimination to successfully describe OC PK. Influenza infection did not affect model parameters, but anesthesia did. The conclusion that OC PK was not influenced by influenza infection must be viewed with caution because the influenza infections in the studies included here resulted in mild clinical symptoms in terms of temperature, body weight, and activity scores. Monte Carlo simulations were used to determine that administration of a 5.08 mg/kg dose of oseltamivir phosphate to ferret every 12 h for 5 days results in the same median OC area under the plasma concentration-time curve 0–12 h (i.e., 3220 mg h/mL) as that observed in humans during steady state at the approved dose of 75 mg twice daily for 5 days. Modeling indicated that PK variability for OC in the ferret model is high, and can be affected by anesthesia. Therefore, for proper interpretation of PK/PD data, sparse PK sampling to allow the OC PK determination in individual animals is important. Another consideration in appropriate design of PK/PD studies is achieving an influenza infection with pronounced clinical symptoms and efficient virus replication, which will allow adequate evaluation of drug effects.